Extension workflow
Fix file extensions in bulk
Wrong extensions make files open in the wrong app or fail validation. Renamio helps repair extension names while keeping the actual file content unchanged.
What usually goes wrong
- Exports may produce uppercase, missing, or wrong suffixes.
- Changing extensions manually is risky in mixed folders.
- Renaming an extension is not the same as converting a file.
Renamio workflow
- 1Filter the files that need extension repair.
- 2Use extension-focused rules or replace rules carefully.
- 3Preview how apps will see the final suffix.
Why this workflow helps
- Cleaner file type labels
- Less manual suffix editing
- Safer preview before changing many extensions
Good fit
- Export folders
- Mixed downloads
- Dataset cleanup before import
Not the right fit
- Converting image formats
- Repairing corrupt files
- Detecting true MIME types for every file
Related rename tools
Extension repair
Fix incorrect file extensions
Detect real file types and fix misnamed extensions such as zip111, rar001, and damaged archive suffixes.
Name cleanup
Clean invalid characters in file names
Remove invalid characters, bracketed text, repeated spaces, and repeated separators from downloaded or exported file names.
Advanced matching
Rename files with regular expressions
Use regex capture groups to restructure file names, clean dates, extract numbers, and rename complex batches safely.
Related guides
Cleanup workflow
Clean invalid file names for Windows and macOS
Remove invalid characters, normalize spaces, and make file names safer before moving files between Windows, macOS, and cloud drives.
Open guideSpreadsheet workflow
Batch rename files with Excel or CSV
Plan batch file names in a spreadsheet, then use Renamio workflows to preview, apply, and audit large rename batches.
Open guideFAQ
Does changing .png to .jpg convert the image?
No. It only changes the file name suffix. Use a converter when the actual format must change.
Can I protect extensions in other rename rules?
Yes. Many Renamio workflows can focus on the base file name while keeping the extension in place.
Preview the rename before changing files
Use Renamio locally on Windows or macOS to test the naming pattern, catch collisions, and keep rename history for review.